Wind turbines are used to produce electrical energy using a renewable resource and without combusting a fossil fuel. Generally, a wind turbine converts kinetic energy from the wind into electrical power. A horizontal-axis wind turbine includes a tower, a nacelle located at the apex of the tower, and a rotor having a plurality of blades and supported in the nacelle by means of a shaft. The shaft couples the rotor either directly or indirectly with a generator, which is housed inside the nacelle. Consequently, as wind forces the blades to rotate, electrical energy is produced by the generator.
On certain occasions, it may be desired or required to inspect, repair, and/or test wind turbine blades after having been installed, and perhaps operated for a certain period of time. Because the blades are elevated above the ground, by as much as 50 or 60 meters to just reach the blade tip, an external mobile crane is often used to provide access to the blades. In this regard, the crane may include a personnel carrier (e.g., a basket) for transporting maintenance personnel and equipment to and from the blades in order to conduct the desired or required task. For example, to test a blade under load conditions, a crane lifts personnel up to the blade for installing equipment that applies a load to the blade.
Such a system, however, has a number of drawbacks. First, the need for an external crane to perform the task significantly increases the cost of the maintenance project. In this regard, crane rental is generally cost prohibitive and may be the greatest contributor to cost for the entire maintenance project. Second, some wind turbines may be located in remote areas which may be difficult to reach with a generally large, mobile crane. Additionally, moving personnel and equipment from the ground to the blade may raise safety precautions and may further be time consuming, as the crane must typically make multiple lifts in order to achieve the desired result (e.g., make the repair, conduct the test, etc.). Furthermore, the number of personnel for the project may be relatively large. For example, three or more workers are typically currently needed in projects such as these, which further increase costs.
Accordingly, there is a need in the wind turbine industry for a device or apparatus for applying a load to an installed wind turbine blade and a method for applying a load to a wind turbine blade that avoids the need for an external crane or other costly hoisting devices.